The 7th JSAP Research Achievement Award
Yasuharu Suematsu

Eiichi Maruyama

Pioneering research in Semiconductor
Lasers for Optical Fiber Communications

Pioneering research in high-performance
imaging devices using non-crystalline
semiconductors

Yasuharu Suematsu was the first in the world to
advocate the importance of transmission methods
using single-mode fibers and lasers that can dynamically maintain single modality as a leading approach toachieving broadband optical fiber communications. He conducted research
into GalnAsP/InP lasers that oscillate in the 1.5-1.6µm band, which minimizes
transmission losses in optical fibers, and in 1979, he became the first in theworld to achieve low-threshold operations and continuous operations at roomtemperature.
To develop a “Dynamic single-mode laser” that can maintain single
modality even with direct modulation at 1GHz or more, he focused on a laser
realization that uses distributed Bragg reflection, and achieved continuousoperations at room temperature in the L.5-1.6µm band for the first time in
1981. In 1982, he pointed out for the first time that wavelength variations
during direct modulation in “Dynamic single-mode lasers” was due to variations in the carrier density on the active layer, and in 1985 he demonstrated
the relationship between optical fiber transmission bands and the factors inwavelength variation in semiconductor lasers. These achievements represent
substantial contributions to the building of scientific foundations that areessential to practical applications of optical fiber communications and to thetransition to ultra-broadband. In 1983, he became the first in the world todevelop a wavelength tunable laser that could continuously control wavelengths using electrical methods by separating the active region of “Dynamicsingle-mode lasers” and a wavelength control region, thereby demonstrating
the potential of optical integrated circuit methods in the context of large
capacity optical fiber communication with wavelength multiplexing.
In this way, Dr. Suematsu has demonstrated outstanding achievements inthe pioneering development of the high-performance lasers that are essential to optical fiber communications, which support the advanced informationsociety, and at the same time has made great contributions to the semiconductor material characteristic and process fields using optical electronics, andto the development of applied physics as a whole.
Dr. Suematsu’s pioneering research in lasers for optical fiber communications, and his training of researchers in this field have both accelerated
and strengthened related research in Japan, and have formed the foundations for dramatic contributions on a worldwide scale. Some of the seeds of
optical fiber communications are reaching their maturity, but the dynamic
single-mode lasers and wavelength tunable lasers that were the focus ofDr. Suematsu’s work are expected to play an important role in future applications such as quantum information communications, optical information
processing, and various forms of optical sensing, and will no doubt havean enormous effect on the future development of applied physics. Theseoutstanding achievements are truly worthy of the JSAP Research Achievement
Award.

From the latter half of the 1960s to through to theearly 1970s – the dawning of the development of TV
image pickup tubes, Dr. Eiichi Maruyama was working
on research in original image pickup tubes using selenium non-crystalline semiconductors, and developed an image pickup tube
that demonstrated truly outstanding characteristics. This technology wasutilized in video cameras for use both in broadcast stations and in the home,and received a high degree of recognition as an original Japanese technology.
This technology was also used in the development of high-definition TV,
which was still in the early stages of research, and in program production forexperimental broadcasts, thereby making notable contributions to the evolution and establishment of high-definition TV. It has also been used in x-ray
imaging, enabling real-time observation of the movement in lattice defects,
which represents a great contribution to science as well.
In the image pickup tubes developed by Dr. Maruyama, the resistance ofphotoconductive semiconductor film is changed in response to the strengthof the incident light; this is read by a scanning electron beam and used as
the image signal. Dr. Maruyama continued his attempts to control the photodiode contact characteristics of selenium non-crystalline semiconductors andto control electrical and heat characteristics by adding impurities, eventually
discovering that it was possible to achieve outstanding photoconductive characteristics using 3-dimensional materials with tellurium and arsenic added.
He also developed a graded structure that controlled component distribution on the nanometer level, as well as a method for forming this construction, thus overcoming the fatal flaw of images being burned onto the screen,
which had occurred with earlier image pickup tubes. In 1973, with the assistance of joint researchers and based on the research results outlined above,
he successfully developed an image pickup tube that demonstrated themost outstanding characteristics of that era, including high sensitivity, low
noise, low residual images, and low level of flickering. The development of
non-crystalline semiconductor film with graded composition distribution uses
computer-controlled thin-film growth methods that were still undeveloped atthat time, so this research could also be considered pioneering research in thefield of material investigation using combinatorial methods.
With the later development of CCD imaging elements, most video
cameras used by broadcast stations and in the home converted to CCDtype, but image pickup tubes using non-crystalline photoconductive film
offer advantages in the detection of areas with high-energy photons (suchas X-rays), so are still used even today, for example in facilities conducting
research in synchrotron radiation.
Dr. Maruyama’s research in image pickup tubes was carried on by otherresearchers, and later became the foundation for the birth of ultra highsensitivity avalanche photomultiplier image pickup tubes. These photomultiplier image pickup tubes enable clear images to be captured even in very
dark environments, so are used in a wide range of observation applications,
including filming incidents in the dark, observations of deep-sea life and otherecosystems, filming of weak auroras, microvascular imaging, and analysis ofthe structure of proteins. Dr. Maruyama also made a joint proposal in 1979
– the first of its kind in the world – regarding a technology for forming low
temperature poly-silicon TFTs on a glass substrate as a means of forming animage display panel and peripheral circuits on a single substrate. He has madenotable contributions to the operation of organizations for promoting fundamental and investigative research, and in the execution of government policy
on science and technology.
Based on the development of original thin-film technologies, Dr.
Maruyama has created outstanding imaging devices, and has made exceptional contributions to science, society, and industry. For these reasons, he istruly worthy of the JSAP Research Achievement Award.

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JSAP International No.16 (July 2007)